In the past, vortex mixers have been used to mix pigment and vehicle in liquids such as paint, typically in 5 gallon cylindrical containers. Such vortex mixers achieved mixing by spinning the container on its cylindrical axis, while that axis was positioned at an angle to a central orbit axis about which the container was simultaneously orbited as well as spun. While such vortex mixers have enjoyed a degree of popularity, they have also been subject to a certain amount of imbalance, caused by a range of density and viscosity in the materials (typically liquids) being mixed. While a vortex was created in the material being mixed, the vortex assumed different shapes and positions within the container, depending upon the density and viscosity of the material being mixed and the spin and orbit speeds of the mixer. While most applications of the present invention contemplate that the materials to be mixed are liquid, other materials may be considered, and, in the event of non-liquid materials (such as granular materials) a concept of apparent or equivalent viscosity would be relevant thereto.
Some prior art mixers had a center of volume offset from the center of rotation such that the center of mass was displaced in one direction with an empty machine, and the center of volume was displace in an opposite direction, such that adding a mass of material to be mixed brought the rotating elements somewhat into balance. However, such balance was only achieved with one volume, density and viscosity of material to be mixed.
Imbalance in prior art mixers manifested itself in vibration of the mixer, sometimes resulting in the mixer “walking” or moving laterally across the surface upon which it was supported. Such walking is undesirable, particularly when the mixer is located on a surface elevated above a floor, as for example, when the mixer is “stacked” on top of other equipment as is sometimes done in paint mixing facilities.
The present invention relates to various aspects of and improvements to the suspension shown and described in copending application Ser. No. 10/891,446, assigned to the same assignee hereof. The suspension provides improved performance for vortex mixers of the type described herein. In alternative embodiments, various pivoting support embodiments may be found useful in the practice of the present invention, along with an annular damper formed of visco-elastic polymer, which has been found to be a desirable embodiment and is included herein. Improved spring mounting arrangements are also included herein.